Israel has strong intelligence links to the neighbouring Sinai, where the Airbus came down on October 31 while en route from Sharm el-Sheikh to Saint Petersburg.
Israeli Defence Minister Moshe Yaalon spoke about the crash to local journalists and his spokesman confirmed the comments to AFP.
"There is a strong probability that this is an attack," Yaalon said. "From what we know and what we understand, I would be surprised if it turns out that it was not an attack."
Britain and the United States, as well as international investigators, suspect a bomb exploded on board, but Egyptian officials insist there is no evidence yet of an attack on the plane.
If IS was behind the attack, it would be the first time the jihadists, who control large areas of Syria and Iraq, have hit a passenger plane.
The IS affiliate in Egypt is waging a bloody insurgency in north Sinai that has killed hundreds of policemen and soldiers.